1. Field of the Invention
The present invention relates to transport and storage containers for liquids with a pallet-like underframe of an electrically conductive material, an exchangeable inner container of synthetic material with four side walls, a bottom wall and a top wall, a closable inlet opening at the top and a lower outlet opening with a draining device, and an outer casing formed of grating or sheet metal.
2. Description of the Related Art
When liquid containers of this type known from DE 195 11 723 C1 are filled and emptied and when liquids are stirred in this type of containers, for example, for mixing purposes, electric charges may occur as a result of liquid friction. The principal danger of electrostatic charging is the fact that ignition sources come into contact with explodable mixtures of gases and vapors.
Because of the electrostatic charging capability, transport and storage containers of the above-described type cannot be used in explosion-endangered rooms and cannot be filled with explosive liquids.
EP 0 699 599 A1 describes an electrically grounded packing container for storing and transporting solid, liquid and pasty products, wherein the container can be used as a self-supporting container or as an inliner or inset container for use in supporting outer containers, such as corrugated cardboard boxes, wood boxes, grate box pallets or drums. The packing container is composed of a multiple-layer composite foil combination which is constructed from a polymer foil with locking layer properties serving as the external layer of the container, an intermediate layer of an electrically conductive material and another polymer foil forming the inner layer of the packing container. The inner layer of the packing container is perforated, so that electrostatic charges which collect in the filling material can flow through the openings provided in the inner layer to the electrically conductive intermediate layer which is in connection through electrical contact points to a grounding system.
EP 0 014 491 A1 discloses a double-wall storage tank for combustible liquids, wherein the storage tank includes an outer wall of steel and a monitoring chamber which is constructed as an inner wall of synthetic material and can be connected to a leakage indicating device which can be operated at excess pressure or negative pressure. For electrically grounding the storage tank, the inner wall surface of the inner wall of synthetic material which faces the storage liquid is covered with a metal wire grating of the type of a Faraday cage which is connected to a grounding terminal in the tank cover of steel.
The electric grounding of the packing container known from EP 0 699 599 A1 which is constructed as a composite layer container by providing an intermediate layer of an electrically conductive material, as well as grounding of the double-wall storage tank in accordance with EP 0 014 451 A1 by a wire grating placed on the inner surface of the inner wall of synthetic material, are both technically complicated solutions.